456 Scientific Intelligence. 



10 _8cm , which is in excellent accord with the values obtained by 

 entirely independent methods. It is far more interesting and 

 important to note that the wave-lengths of the secondary X-rays 

 are of the order of 2xl0~ 9cm . More precisely, Laue evaluates 

 five wave-lengths whose coefficients of io~ 9cm are respectively 

 1*27, 1*90, 2*24, 3*55, and 4*83. These numbers have approxi- 

 mately the ratios of the integers 4": 6:7: 11: 15. It should be 

 remarked, in conclusion, that the solutions are not single valued, 

 and that the interference figures obtained by Friedrich and Knip- 

 ping have been accounted for by W. L Bragg on a somewhat 

 different assumption concerning the distribution of atoms in the 

 molecule, and by considering reflections from planes of atoms. 

 The two theories, however, differ chiefly in the point of view and 

 mode of attack, but fundamentally they amount to very much 

 the same thing. — Sitzungsber. d. K. Bay. Akad. d. Wiss., Mtin- 

 chen, June, July, 1912. h. s. u. 



4. Researches in Colour Vision and the Trichromatic Theory / 

 by Sir William de W. Abney. Pp. xi, 418, with 100 figures 

 and 5 plates. London, 1913 (Longmans, Green and Co.). — The 

 author has brought together in book form the substance of a 

 comparatively large number of communications on the subjects 

 of color photometry and color vision, which he has made to the 

 Royal Society during the last twenty-five years. A reference 

 list of twenty-nine of these papers is given just before the index. 

 The most cogent reason for issuing this work is the author's 

 desire ":. . .to show that the Trichromatic Theory of Colour 

 Vision does not yet require a funeral oration over its remains." 

 "It is not by any means as moribund as some seem anxious it 

 should be considered, but is, in fact, very much alive." 



The volume is divided into two Parts, of which the first is 

 elementary and deals with such subjects as the eye, phenomena 

 of vision, spectral colors, luminosity, color discs, etc. It is 

 designed as an introduction to the more specialized and advanced 

 portions of the text. The main subject of Part II is color vision 

 and hence it treats of the physical theory of color vision, of color 

 sensations, of congenital and other forms of color blindness, of 

 retinal fatigue, and so forth. The author does not criticize any 

 rival theory but confines himself to an account of his own 

 researches. This book is an extremely important contribution to 

 the subject, and it will undoubtedly be heartily welcomed by 

 physicists, physiological psychologists, ophthalmologists, and 

 others. The colored plates are beautifully tinted and no improve- 

 ment in the typography seems possible. (However, in fairness 

 to the lay reader, it should be remarked that the statement on 

 page 3, to the effect that the number of pairs of spectra which a 

 diffraction grating can produce is theoretically infinite, is incor- 

 rect.) h. s. u. 



5. Radium and Radioactivity, (Romance of Science Series) ; 

 by A. T. Cameron. Pp. 185, with 23 figures. London, 1912 

 (The Society for Promoting Christian Knowledge). — A sufficiently 



